The invention relates to alloys based on lead and antimony containing less than 4% by weight of antimony intended for use as supports for electrodes of lead accumulators.
It is known, particularly from Japanese Pat. No. 37-5552 filed Aug. 25, 1960 by the Furukawa Battery Co. Ltd. to introduce a rare earth, particularly cerium, into alloys to improve the fineness of the grains and thus reduce the risks of cracking of the supports. It is also known, particularly from French Pat. No. 78 21 502 filed July 20, 1978 by the Applicant, to introduce into the lead-antimony alloy not one rare earth, but a mixture of rare earths, for example misch metal, the total content of the mixture of rare earths being between 0.001 and 1%.
This characteristic has the effect that, if the electrode supports are fabricated at a temperature corresponding to the melting point of the alloy in a crucible, in order to obtain an equivalent grain size, it is necessary to work at a temperature of about 500.degree. C. with cerium, but with misch metal one can work at a temperature on the order of 420.degree. C.
At 420.degree. C., in fact, it is possible to introduce into the alloy more misch metal than cerium and thus obtain a better fineness.
In other words, in order to permit the introduction of a more significant amount of cerium to obtain the same grain size as with misch metal at 420.degree. C., it is necessary to raise the fabrication temperature of the supports.
Now any elevation of the fabrication temperature leads, on the one hand, to an increase in the consumption of energy and, on the other hand, to the risk of deterioration of the alloy by oxidation.
At 420.degree. C., it is possible to introduce into the alloy about:
20 ppm (0.002%) of cerium, or PA0 50 ppm (0.005%) of lanthanum, or PA0 50 ppm (0.005%) of praseodymium or PA0 100 ppm (0.01%) of misch metal.
At this temperature, with cerium, lanthanum and praseodymium, there is obtained an average diameter of the grains lying between 200 and 250.mu., whereas with misch metal, the average diameter is on the order of 130.mu..